It is well known in the art to provide wheel covers for wheels in a vehicle, such as an automotive vehicle, to enhance the appearance of the wheels. Wheel covers are typically secured to a wheel using conventional devices. For instance, many wheel covers include a plurality of circumferentially spaced openings adapted to receive a lug nut. The lug nut typically has a flange. The spaced openings have extensions that can be snapped to the flange of the lug nut. The extensions are axisymmetrical, or all are stressed or preloaded uniformly, to secure the wheel cover on the wheel.
While the wheel cover may be secured to the flange of lug nuts of the wheel, there are several problems with the conventional designs. First, securing wheel covers to lug nuts using conventional securing devices requires a great deal of effort. Fitting the retention legs over the lug nut is often difficult and requires substantial force. Additionally, removing wheel covers also requires a great deal of force, often resulting in damage to the wheel cover or wheel. Conventional wheel covers can account for tolerance, by providing an excessive interference fit with the lug nut.
Essentially, existing snap-on, secured wheel covers retained by lug nuts with features molded into the wheel cover are over-designed with heavy sections and high preload settings or interference fit. Conventional designs attempt to compensate for lug nuts and wheel cover assembly tolerance stack-ups. The heavy sections and high preloads result in excessive installations and removal efforts which are significant design shortfalls.
An additional problem with existing wheel covers includes creep. Creep is the time-dependent part of permanent strain, or plastic deformation, resulting from stress. Typically, creep occurs when a plastic part is subjected to a load for a long period of time. Creep degrades retention performance and can create looseness of the secured wheel cover over time. This is especially problematic at higher temperatures. Obviously, with the preloaded fit of the wheel cover over the flange of the lug nut, once the wheel cover begins to creep the wheel cover nominal preload is reduced degrading retention performance and the wheel cover can become loose. This results is an insecure wheel cover, which can rattle during driving or become detached.
Indeed, existing designs account for “loose fit” tolerance stack-up by increasing nominal interference fit (i.e. preload) on all engagement or retention legs. This substantially degrades post durability retention performance (i.e. creep test, peak temperature test, etc.) and results in exceedingly high installation and removal efforts. The various embodiments of the present invention can account for root sum of squares “loose fit” tolerance stackup between the wheel cover and lug nut features (i.e. the wheel cover fit is tight with two or more −3 sigma “loose fit” wheel nuts) without the need for nominal interference fit on the majority of retention engagement legs.
Thus, there is a need in the art for an improved wheel cover enabling easier installation and removal. Further, there is a need for an improved wheel cover that improves resistance to creep. There is also a need for an improved wheel cover providing a snug fit of the wheel cover to the wheel for all wheel nut sizes and position manufacturing variations.